1. Field of the Invention
The invention relates to a double mass flywheel. More specifically, the present invention relates to a double mass flywheel having a first flywheel fixed to a crankshaft and a second flywheel connected to a crankshaft through elastic members.
2. Background Information
Conventionally, a flywheel is attached to a crankshaft of an engine for absorbing vibrations caused by variations in engine combustion. Further, a clutch device is usually arranged on a transmission side (i.e., in a position axially shifted toward the transmission) with respect to a flywheel. The clutch device usually includes a clutch disk assembly coupled to an input shaft of the transmission, and a clutch cover assembly for biasing the frictional coupling portion of the clutch disk assembly toward the flywheel. The clutch disk assembly typically has a damper mechanism for absorbing and damping torsional vibrations. The damper mechanism has elastic members such as coil springs arranged to compress in a rotating direction.
A structure is also known in which the damper mechanism is not arranged in the clutch disk assembly, and rather is arranged between the flywheel and the crankshaft. In this structure, the flywheel is located on the output side of a vibrating system, in which the coil springs form a border between the output and input sides, so that inertia on the output side is larger than that in other prior art. Consequently, the resonance rotation speed can be lower than an idling rotation speed so that damping performance is improved. The structure, in which the flywheel and the damper mechanism are combined as described above, provides a flywheel assembly or a flywheel damper, an example of which is disclosed in Japanese Unexamined Publication H04-231757, which is hereby incorporated by reference. The flywheel fixed to the crankshaft of the engine is called a first flywheel, and the flywheel connected to the crankshaft via the elastic members is called a second flywheel.
The friction generation mechanism is located to operate in parallel with the elastic members of the damper mechanism in the rotational direction. When the second flywheel rotates relative to the crankshaft, the elastic members of the damper mechanism are compressed in the rotational direction and the friction generation mechanism generates frictional resistance. As a result, torsional vibrations due to the combustion fluctuations of the engine are quickly dampened.
The friction generation mechanism may have a friction generation portion and a rotational engagement portion functionally located in series with the friction generation portion in the rotational direction. The rotational engagement portion is made of two members defining a minute rotational gap between them. Accordingly, when the minute torsional vibrations occur due to the combustion fluctuations of the engine, the two members do not abut each other in the rotational engagement portion so as not to operate the friction generation mechanism. As a result, the torsional vibrations are effectively absorbed or dampened.
The friction generation mechanism is likely to be affected by heat from the clutch friction surface of the second flywheel. If the friction generation mechanism is held by the second flywheel side member, the fiction performance is not stable. For example, the friction coefficient is changed due to the exposure of the friction generating mechanism to heat.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved double mass flywheel. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.